Geochemistry of Rare Earth Elements in Coal—A Case Study from Chongqing, Southwestern China

Abstract

The contents and distribution patterns of rare earth elements (REEs) in coals of different geological periods from Chongqing were studied. The results show that the REE content in coals from Chongqing is 165 µg/g, much higher than that of the common Chinese coals, US coals, and the worldwide coals. The concentration of LREE is much higher than that of the heavy ones. However, the ratio of LREEs to HREEs is only 5.11, much lower than that of the ordinary coals from China. There are two types, A and B, of distribution pattern of rare earth elements in coal. The main distribution pattern is A. The distribution pattern of rare earth elements in Sinian and Cambrian stone coals and Early Permian coals is B, and it is dominated by A and followed by B of the Late Permian and Late Triassic coals. In addition, sequential chemical extraction experiments indicated that silicate association dominates the modes of occurrence of REEs in coals from Chongqing.

Rare-Earth Element Phase Associations in Four West Virginia Coal Samples

“…Several studies have used the technique to identify REY phase associations in coal and coal-related strata. Li et al [59] targeted REY in the carbonate, organic, silicate, sulfide, exchangeable, and water-soluble phases in Chinese coals of varying geologic ages. They concluded that the majority of REY were associated with silicate minerals [59].…”

“…Li et al [59] targeted REY in the carbonate, organic, silicate, sulfide, exchangeable, and water-soluble phases in Chinese coals of varying geologic ages. They concluded that the majority of REY were associated with silicate minerals [59]. A study on Appalachian Basin coal underclays and coarse refuse examined REY in watersoluble, exchangeable, acid-soluble, reducible, and oxidizable fractions [60]; however, less than a quarter of TREY were recovered from the samples.…”

Rare metal elements in the primary coal seam of Changzhi coalfield in Southeast Shanxi, China

“…contain La and Th (as shown in Figure 8), suggesting that the REEs and Th are correlated with clay minerals. Studies show that the REEs may correlate with clay minerals (e.g., kaolinite, illite), organic matter and independent mineral containing REEs (Dai et al, 2005;Li et al, 2005). REEs (especially LREE), Ga, and Th are incompatible elements and can occur in small amounts adsorbed in a mineral crystal lattice.…”

“…The distribution of trace elements in coals can provide geological information, such as depositional conditions, coal-bearing sequence formation, and regional tectonic history, because their distributions are determined by the processes of peat accumulation and coal rank advance, as well as interaction with the organic matter, basinal fluids, sediment diagenesis, and synsedimentary volcanic inputs. Recently, several researchers in China have studied the geochemistry characteristics, occurrence model, and geological control factors of REEs in coal deposits in different regions of China (e.g., Huainan, Huaibei, South China, and Chongqing) as well as in the different coal forming periods, prompting discussion on the microenvironment of REEs in coal deposits (Du and Zhuang, 2006;Li et al, 2005Li et al, , 2018Wang et al, 2002;Zhao et al, 2000aZhao et al, , 2000b). Previous studies showed that the concentration of REEs in coal deposits can be up to 300 À 1000 lg/g in the far east of Russian (Finkelman et al, 1990) and 500 À 4000 lg/g in Fire Clay, the America East (Seredin, 1996), respectively; the concentration of REEs in coal deposits in the Sydney Basin in Nova Scotia, Canada, is 72 À 483 lg/g and is mainly deposited in silicate minerals, which are mainly from terrestrial detritus or marsh solution (Birk and White, 1991).…”

Geochemistry of rare earth elements and yttrium in a Ge-poor coal from the Wulantuga ore deposit, Inner Mongolia, North China

“…Yttrium and rare earth can be used as geochemical indicators in coal and coal-bearing strata because they own relatively stable geochemical characteristics during different geological processes (Li et al 2005). Yttrium and rare earth may provide significant information for the study of terrigenous areas and oxidation-reduction environment of peat accumulation, history of tectonic evolution, volcanic ash eruption, and hydrothermal solution activities.…”